Support `void` class lookups in `ReflectionUtils`

[bjmi]

Running following parametrized test in JUnit 5.11

@ValueSource(strings = {
    "void", "boolean", "byte", "char", "short", "int", "long", "float", "double" })
@ParameterizedTest
void isPrimitive(Class<?> candidate) {
    assertTrue(candidate.isPrimitive());
}

only makes the "void" case fail.

org.junit.jupiter.api.extension.ParameterResolutionException:
    Error converting parameter at index 0: Failed to convert String "void" to type java.lang.Class

It looks like conversion of "void" to Class isn't supported.
Both classNameToTypeMap and primitiveToWrapperMap of org.junit.platform.commons.util.ReflectionUtils are lacking void.class and Void.class, but maybe this is by intention.

[marcphilipp]

Did you deliberately not use the classes attribute?

@ValueSource(classes = { void.class, ... })
@ParameterizedTest
void isPrimitive(Class<?> candidate) {
    assertTrue(candidate.isPrimitive());
}

That being said, I see no reason not to add support for "void"

[sbrannen]

Both classNameToTypeMap and primitiveToWrapperMap of org.junit.platform.commons.util.ReflectionUtils are lacking void.class and Void.class, but maybe this is by intention.

If my memory serves me correctly, it was indeed intentional since void and Void are not real types but rather pseudo-types.

And since we never had a concrete use case for supporting conversions for those in JUnit itself, we didn't introduce those mappings.

Though, I agree with @marcphilipp that it should be fine to add lookups for those in ReflectionUtils.

[bjmi]

Did you deliberately not use the classes attribute?

I quickly switched to classes when strings didn't work.